Native Defects Hybridization and Electronic Transport in Cu2Se‐CuGaSe2 Hierarchical Composites

Engineering the energy distribution of electronic defects in semiconductors can afford the coexistence of degenerate and nondegenerate transport behavior. By leveraging native defects in Cu2Se and CuGaSe2 phases, the tunability of the concentration and energy distribution of active electronic defects in hierarchical (1‐x)Cu2Se‐(x)CuGaSe2 composites is demonstrated. This study found that the electrical conductivity of various composites decreases with rising temperature indicating degenerate semiconducting behavior, whereas the carrier density increases with temperature, which is consistent with non‐degenerate semiconductivity. Remarkably, this study found that while the carrier density and electrical conductivity drop with the increasing CuGaSe2 content for samples with x ≤ 0.45 is consistent with an increase in the activation energy of “active” electronic defects, the sudden increase by 140% in the electrical conductivity and by 109% in the carrier density for near equimolar composition suggests the formation of a large density of electronic defects with lower activation energy. This unusual behavior is understood within the context of the hybridization of coexisting native electronic defects to form degenerate hybrid acceptor states with lower activation energy. The reported unique electronic transport can be leveraged for the development of more versatile electronic and optoelectronic devices with superior performance. Mutual atomic to micrometer scale hierarchical structural integration of Cu2Se and CuGaSe2 phases enables strong entanglement of their electronic structure leading to hybridization of their native electronic defects for nearly equimolar composites.